This application requests support to continue the program of Psychobiological research in the Department of Psychiatry, Emory University School of Medicine. The School of Medicine together with the Georgia Mental Health Institute wish to support a comprehensive research program that is basic to problems of brain function, behavior, and mental health. The aim is to investigate the physiological and, in particular, the neuroendocrine bases of patterns of primate behavior; especially on affectional and sexual responses and on agonistic and aggressive responses. The three interrelated studies proposed here with a social primate, namely, the cynomolgus monkey, are concerned with elucidating some of the factors and brain mechanisms responsible for the close relationship between sexual and aggressive arousal that exists in birds and mammals, including non-human primates and the human. Study I will use well-established ethological techniques to examine systematically for the first time in a male primate how 4 ubiquitous variables (prior sexual and aggressive arousal, ability to obtain sexual consummation with the partner, presence of an alternative target for male aggression) affect the pair-bond by changing the severity and amount of aggression directed by males at females. Medroxyprogesterone acetate (MPA) is a sexual behavior in men, and Study II will employ behavioral and neuroendocrine techniques to determine its mechanisms of action and its effects on the sexual and aggressive behavior of male cynomolgus monkeys. Study III will utilize autoradiographic and biochemical methods to examine in more detail how MPA interacts with structures in the primate brain by studying its neural localization and binding sites. This study will further examine interactions with progestin receptors and with the understanding of the metabolism of testosterone in the brain. Taken together, this research will help our understanding of the mechanisms regulating aggression by male primate towards their female partners and this will contribute new information of forms of violence that currently represent major problems in society.